The present invention relates generally to loudspeaker cones, and more particularly to a novel loudspeaker cone assembly and method for making same.
Loudspeaker cones, alternatively termed loudspeaker diaphragms, are well known which employ a fibrous or felted paper-type cone or diaphragm adapted to be supported on a support frame through an annular suspension member or rim secured to the outer marginal edge of the cone and having predetermined elastic or flexibility properties. The suspension member or rim may be formed as an integral generally radially directed extension of the periphery of the cone or diaphragm, as disclosed in U.S. Pat. Nos. 1,872,583, 2,302,178 and 4,646,874, or may be formed as a separate annular supporting flange or rim affixed to an outer peripheral edge of the cone, such as disclosed in U.S. Pat. Nos. 2,840,177 and 3,684,052. Alternatively, the loudspeaker cone or diaphragm may be formed of plastic material such as disclosed in U.S. Pat. No. 3,858,680.
With the advent of relatively sophisticated sound reproduction systems, such as in stereophonic sound systems, the dynamic or moving coil-type loudspeaker cones used for the mid and low frequency ranges are subjected to relatively high amplitude vibrations in the axial direction of the cone. In the past, many manufacturers of larger size loudspeaker cones have made the suspension rims from rubber in order to achieve desired flexibility and durability. A drawback to the use of rubber suspension rims is their relative high cost.
To overcome the higher cost of rubber speaker cone suspension rims, attempts have been made to manufacture the suspension rims from plastic foam material. One method for making plastic foam-type suspension rims entails cutting a bulk block of raw foam material into slices or sheets of predetermined thickness. A foam sheet is then placed between heated dies which form an annular rim after which the rim is affixed to the outer edge of a cone, generally by means of an adhesive or sewing. This technique has not been totally successful because the rims generally have insufficient strength integrity to support larger diameter speaker cones. A suspension rim made from a double layer of such foam sheets in a laminated construction by a similar heated die process was found to provide improved suspension rims.
A drawback to all known prior methods or techniques for making loudspeaker cone suspension rims is that they do not facilitate economical manufacture of rims in small lots of different colors, as may be desired for various applications.
Thus, a need exists for a loudspeaker cone assembly having a suspension rim which exhibits desired strength, flexibility and durability and which is economical to manufacture. Further, a relatively low cost suspension rim which has high strength adhesion to the rim of the speaker cone and which can be economically manufactured with various surface colors would find wide acceptance.